Move over standard model – possible evidence for an unpredicted new particle found

In July 2012, physicists at CERN announced something amazing – the discovery of the Higgs boson, a previously undetected particle predicted by the standard model. Now some more exciting and surprising evidence has come to light.

The Large Hadron Collider has been closed since December 2015 for maintenance, so scientists at CERN have been reanalysing their data, and have found something odd. A cluster of photons, or a diphoton excess, has been detected in a previously ignored energy range. It suggests that a new particle has been created, with a mass of around 750 times the mass of a proton. It is most probably a boson, a particle associated with fundamental forces.

What’s even more surprising is that this particle isn’t predicted at all by the standard model. If the particle has been created, a whole new model would have to be constructed. This would be very exciting for theoretical physicists, because it might also be able to explain other mysterious phenomena, like the existence of dark matter and why there is more matter than antimatter. Many possible replacement models have already been put forward by theoretical physicists, such as the mathematical theory of supersymmetry which suggests that the particle is like a neutrino, but heavier and spin zero.

When the LHC is restarted this month it will run with higher energies and more collisions per second, so the potential particle can be investigated further. The current evidence has the same strength as the evidence for the Higgs boson 6 months before it was announced, that’s one to two sigma. Five sigma are needed to provide enough evidence to be accepted – a three in 10 million chance that the signal is a fluke. What makes this evidence good enough for CERN to publish early is that two independent teams, ATLAS and CMS, have both detected a signal supporting the particle.

Don’t get too excited yet – the evidence may all just be a coincidence. If it’s not though, this could change particle physics as we know it. The team at CERN think that they’ll know by the end of this summer.

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